net/can: can protocol uses a separate buffer to cache can data

To avoid memory waste, can add support for using an independent iob buffer
The IP protocol often configures CONFIG_IOB_BUFSIZE to be relatively large,
such as 512, for higher throughput. However, the buffer required by CAN is
fixed at a length of 16 or 64. If the system's IOB is directly used,
a lot of memory will be wasted.

Signed-off-by: zhanghongyu <zhanghongyu@xiaomi.com>

include/nuttx/net/can.h

@@ -44,6 +44,7 @@
 
 #include <nuttx/config.h>
 #include <nuttx/can.h>
+#include <nuttx/mm/iob.h>
 #include <nuttx/net/netconfig.h>
 #include <stdint.h>
 
@@ -126,6 +127,48 @@ extern "C"
 struct net_driver_s; /* Forward reference */
 int can_input(FAR struct net_driver_s *dev);
 
+/****************************************************************************
+ * Name: can_iob_timedalloc
+ *
+ * Description:
+ *  Allocate an CAN I/O buffer from the CAN buffer pool.
+ *
+ ****************************************************************************/
+
+#if CONFIG_NET_CAN_NBUFFERS > 0
+FAR struct iob_s *can_iob_timedalloc(unsigned int timeout);
+#else
+#define can_iob_timedalloc(t) net_iobtimedalloc(true, t)
+#endif
+
+/****************************************************************************
+ * Name: can_iob_clone
+ *
+ * Description:
+ *  Clone an I/O buffer from the CAN buffer pool.
+ *
+ ****************************************************************************/
+
+#if CONFIG_NET_CAN_NBUFFERS > 0
+FAR struct iob_s *can_iob_clone(FAR struct net_driver_s *dev);
+#else
+#define can_iob_clone(d) netdev_iob_clone(d, false)
+#endif
+
+/****************************************************************************
+ * Name: can_iob_navail
+ *
+ * Description:
+ *   Return the number of available CAN I/O buffers.
+ *
+ ****************************************************************************/
+
+#if CONFIG_NET_CAN_NBUFFERS > 0
+int can_iob_navail(void);
+#else
+#define can_iob_navail() iob_navail(false)
+#endif
+
 #undef EXTERN
 #ifdef __cplusplus
 }